Electric shaver with cutters mounted in end to end alignment

ABSTRACT

An electric shaver comprising two cutter sections mounted in aligned end-to-end relationship; the cutter sections being mounted for linear reciprocation in said aligned end-to-end relationship; with substantially the same natural frequency of reciprocation; a driving motor; the driving motor is operable to reciprocate the respective cutter sections in antiphase at said natural frequency of reciprocation.

United States Patent 1191 Wellinger et al. I

[ 1 ELECTRIC SHAVER WITH CUTTERS MOUNTED IN END TO END ALIGNMENT [75]Inventors: Roger Paul Wellinger, Neuchatel;

Francis Andre Vauthier, Hauterive; Alberto Botta, Lausanne, all ofSwitzerland [73] Assignee: The Gillette Company, Boston,

Mass.

[22] Filed: July 20, 1972 21 Appl. 110.; 273,480

[30] Foreign Application Priority Data Dec. 8, 1971 Great Britain56910/71 [52] US. Cl. 30/4332 [51] Int. Cl B26b l9/04 [58] Field ofSearch 30/438, 43.9, 43.91, 43.92, 30/346.5l

[56] References Cited UNITED STATES PATENTS 2,202,203 5/1940 Hill30/4392 3.263.105 7/1966 Heyek 310/29 X Feb-.4, 1975 3,504,433 4/1970Futterer 30/4392 3,750,279 8/1973 Cobarg 30/4392 FOREIGN PATENTS ORAPPLICATIONS 1,005,404 3/1957 Germany 30/34651 1,045,853 12/1958 Germany30/4392 Primary Examiner-Al Lawrence Smith Assistant ExaminerGary L.Smith Attorney, Agent, or Firm-Flynn & Frishauf [57] ABSTRACT Anelectric shaver comprising two cutter sections mounted in alignedend-to-end relationship; the cutter sections being mounted for linearreciprocation in said aligned end-to-end relationship; withsubstantially the same natural frequency of reciprocation; a drivingmotor; the driving motor is operable to reciprocate the respectivecutter sections in antiphase at said natural frequency of reciprocation.

20 Claims, 3 Drawing Figures PATENTED 41975 v sum 2 OF 2 FIG.2

1 ELECTRIC SHAVER wmi cuTTER's MouNTEn lN END To END ALIGNMENT Thisinvention relates to dry shavers for shaving hair from human skin.

SUMMARY OF THE lNVENTlON From one aspect, a dry shaver according to-theinvention comprises two or more cutter sections arranged end to end andoscillatable to and fro along aligned paths, and means operable tooscillate the cutter sections, one or more sections being oscillated in.

antiphase to one or more-others.

Such an arrangement substantially reduces vibration which is otherwisecaused by the oscillating mass of a movable cutter and does so in aparticularly compact manner.

A vibrationally balanced system as described above is applicable tovarious types of cutting heads. In a particular embodiment which will bedescribed, the head may comprise of a stationary outer foil which isperforated and curved and two inner cutter sections each of whichcomprises a plurality of blades mounted on a carrier, the blades beingprofiled so as to match the curvature of the foil, and the inner cuttersections being oscillated along a substantially linear path parallel tothe axis of curvature of the foil.

' Each cutter section is preferably supported on a cutter supportingstructure including one or more resilient members extending generallyperpendicular to said path whereby said cutter and resilient member ormembers can vibrate with the cutter oscillating along said path.

A preferred form of support for the cutter sections comprises tworesilient members spaced apart along the paths of the cutter sections,each of the resilient members having a root end farther from the shaverhead and secured to a fixed part of the shaver and at least two armsextending away from the root end and towards the cutter sections, onecutter section being supported on at least one arm of each of the tworesilient elements and the other cutter section being supported on atleast one other arm of each of the two resilient elements.

Preferably, each of the two resilient elements has three such arms andone cutter section is supported by the two outer arms of eachelement'and the other cutter section is supported by the inner arm ofeach resilient element. Such an arrangement is described in greaterdetail below.

It will be appreciated that a system using cutter sections oscillatingin antiphase along aligned paths may be utilized with various othermanners of supporting the movable cutter sections, and that its mainadvantage of reduced vibration will be obtained irrespective I quency ofboth. The adjustment of resonant frequencies maybe achieved by givingthe supporting resilient members appropriate stiffnesses. Theirstiffness can be varied by varying their cross-sectional area, forexample, or by including stiffening flanges as described in copendingapplication Ser. No. 273,488.

Various driving-means or power sources may be used. Where resonance isrequired and theshaver is intended for operation from AC mains then asynchronous AC motor may be used. This will run always at a constantspeed determined by the mains frequency and so it will be able to drivethe resonant cutter sections at their resonant frequency using a cam orcrank arrangement such as is describedbelow, provided they are tuned toresonate at or close to the appropriate mains frequency.

Alternatively, a DC motor may be employed, fed either from batteriescontained in the shaver casing or from a rectifier circuit fed from themains. A constant speed can be obtained from a DC motor relativelysimply using a back-EMF bridge in association with a power controlamplifier system. Alternatively, a servotype system can be used in whicha tachometer generator is driven by the motor and its output voltage,proportional to the motor speed is compared with a reference to providean error signal for controlling the motor input current. When the motoris thus run at a constant speed it is necessary simply to arrange theresonant systemsof the shaver to match the speed of the motor. This maybe done initially in an approximate fashion and a variable element maybe included so that the motor speed can be varied over a range and canbe manually adjusted within' the range to achieve resonance of thecutter and/or counterweight system.

In battery shavers inparticular, power consumption is an importantfactor in that it determines the length of battery life, or rechargingfrequency and has'an influence on the desired power and hence weight andbulk of the'drive motor to be used. Vibration of the shaver body in use,which is in itself to be avoided for reasons of comfort and noise,canaggravate the power problem which is so important in a batterypowered shaver.

According to a further aspect of the invention there is provided abattery powered electric shaver wherein a battery powered motor isadapted to drive two aligned cutter sections in end-to-end linearreciprocation, respectively in antiphase, wherein the two cuttersections are each supported by a mounting incorporating a spring and thespring constants (K K of the mounting springs are selected in relationto the masses (M M of the respective sections so that KJM issubstantially equal to K- /M whereby the two sections have substantiallythe same natural frequency of reciprocation, and wherein the motor isoperable under power supplied from the battery to drive said movablesections at'a frequency of reciprocation substantially equal tosaidnatural frequency.

It will be understood that the respective spring mountings for the twomovable members may form part of a single spring supporting structure,the spring constants K, and K referring to the repsective parts of saidsingle structure which support the respective movable members.

In order that the invention may be more clearly understood, anembodiment thereof will now be described, by way of example, withreference to the accompanying diagrammatic drawings, in which:

FIG. 1 shows a partly exploded perspective view of two cutter sectionsand their resilient supporting sysversely of the axis of the cutter andhaving curved outer cutting edges: In FIG. 2 a'curved outer cutter isshown in the form 'of a foil 2 which is perforated and the curvature ofwhich matches that of the inner cutter l. The

lateral edges of the foil 2 are secured to fixed parts 3 of the shaver.

The movable cutter sections la and lb are supported so as to beoscillatable along substantially parallel substantially linear paths inantiphase, by means of two resilient members'6 which extendsubstantially perpendicular to the paths of the cutter sections and arespaced apart in the direction of said paths.

Each resilient member 6 has a root end 7 which is secured in a suitablemanner to a fixed part 8 of the shaver. From the root end 7 threesubstantially parallel arms 9 extend towards the shaver head. Theresilient members 6 may each comprise a metal leaf spring, or may bemade from plastic, or may be made by bending spring wire into a formproviding the three arms 9.'The arms 9 may be formed as three separatepieces but the one-piece construction shown is convenient.

The corresponding outer arms 9 of the two resilient members 6 are joinedtogether by longitudinal members l and the two members 10 are linkedtransversely at a region under the cutter'section 1a by means of abridge 11.

The cutter section 1a is supported on the four outer arms 9 of theresilient members 6 by means of a suitable spring mounting l4'which isattached at the centre of the bridge 11 and is indicated in a schematicmanner. Various suitable types of mounting are known. A

similar spring mounting l4 secures the cutter sectionlb to alongitudinal member 16 which joins the two middle arms of the resilientmembers 6. It can be seen in the Figures that longitudinal member 16 hasa downwardly stepped portion 16a which passes under and clear of thebridge 11. The spring mountings 14 are such as to press the cuttersections against the inside of the curved foil 2 and to locate themagainst longitudinal movement relative to the longitudinal members 10and 16 which carry them.

Thus, because of the resilience of the arms 9, which enables them toflex in both directions from their normal position, the cutter sectionsla and lb can be made to oscillate in antiphase along substantiallyparallel substantially linear paths, as indicated by the arrows a and brespectively.

Referring to FIGS. 2 and 3 the power source of the razor is a batterypowered motor 17 which drives a crank shaft 18. The two throws of thecrank shaft 18 are at 180 to each other. The upper throw is cona nectedto a pin 19 mounted under longitudinal member 16 which carriesthe cuttersection lb by means of a connecting rod 20, (see FIGS. 2 and 3). Thelower throw is connected to a pin 21 mounted under the bridge 11carrying. the movable cutter sect-ion la by means of a connecting rod22. The pin 21 passes downwardly through and clear of a longitudinallyextending slot 16b (FIGS. 1 and 2) in the stepped portion 16a of member16. Alternatively, a supplementary bridge for mounting of the pin 21 maybe provided below the bridge vll, the stepped portion of the member 16passing between the two bridges and the requirement for the longitudinalslot 16b being avoided.

Thus, when the electric motor 17 is energized the crank shaftIS rotatesand, because the two throws of the crank shaft are out of phase thelongitudinal members 10 and the longitudinal member 16 are driven to andfro in antiphase with each other, and consequently the cutter sectionsla and 1b respectively carried thereby are also driven along theirsubstantially linear paths in antiphase.

The masses (M M of the cutter sections la and lb will be selected suchthat as they oscillate in antiphase,

linear vibrations are compensated for ascompletely as possible. Thiswill normally mean that their masses should be identical. Also, if thecutter sections la and lb are of similar construction, their centres ofmass will move on the same axis and hence there will be no vibrationalmoment generated.

For resonant operation the resonant frequencies of the two oscillatingsystems are predetermined by suitably relating the stiffnesses (U U ofthe middle and outer arms 9. Their stiffnesses will depend on theirwidths and thicknesses.

The motor is operated to-drive the two oscillating systems at theircommon resonant frequency.

The resilientmembers 6 and the longitudinal members l0 and 16 which jointhem together may be formed integrally from a single piece of metal orplastic material.

Although in the embodiment shown each of the resilient members 6 hasthree arms it is possible for these to have only two arms each, thecorresponding arms of the two resilient members being joined byrespective longitudinal members. The movable cutter sections la and lbcould then be mounted in some suitable manner on respecstive ones of thetwo longitudinal members.

Although only two cutter sections are used in the embodiment described,it will be apparent that three or more cutter sections could be used. Inthe case of three sections a central section could be mounted on acentral bridge such as bridge 11 and two end sections, each half thesize of the central section, could be mounted at opposite ends of thecentral longitudinal member 16.

By using two or more end to end cutter sections oscilmotor shaft to alinear motion, said pair of devicesbeing coupled to said at least twocutter sections for linearly driving said at least two aligned cuttersections in end-to-end linear reciprocation, respectively in antiphase;and 1 support means including mountings coupled to and resilientlysupported each cutter section, each mounting including a spring, thespring constants (K K of the mounting springs being selected in relationto the masses (M M of the respective cutter sections so that VK,/M issubstantially equal to K /M so that the at least two cutter sectionshave substantially the same natural fre quency of reciprocation; saidmotor being operable under power to simultaneously drive said movablecutter sections via said transmission means substantially continuouslyat a frequency of reciprocation substantially equal to said naturalfrequency. 2. An electric shaver according to claim 1, wherein the atleast two movable cutter sections each comprise movable inner cutterscooperating with an outer foil.

3. An electric shaver according to claim 2, wherein said outer foil isstationary.

4. An electric shaver according to claim 1,-comprising two movablecutter sections and wherein said supporting means for the two cuttersections comprises a pair of leaf springs having at least two armsprojecting from a common root, at least one arm being secured at itsfree end to one section and at least one other arm being secured at itsfree end to the other section.

5. An electric shaver according to claim 1, wherein said motor is abattery powered motor.

6. An electric shaver according to claim 1, wherein said pair of devicescomprises a pair of crank throws coupled to said crank.

7. An electric shaver comprising: two cutter sections movably mounted inalignment in end-to-end relationship; 1

means for resiliently mounting the cutter sections for linearreciprocation in said aligned end-to-end relationship, said mountingmeans including resilient structures defining a natural rest positionfor each cutter section at substantially the centre of its path oflinear reciprocation;

driving means including a motor having a rotary output shaft; and

transmission means including a crank coupled to and driven by said motorshaft, said crank having a pair of devices for converting the rotarymotion of said motor shaft to a linear motion, said pair of devicesbeing coupled to said cutter sections so as to substantiallycontinuously and simultaneously linearly reciprocate the respectivecutter sections in antiphase such that the cutter sections linearly movesimultaneously towards and away from each other alternately and alwayspass substantially simultaneously through their said respective naturalrest positions.

8. An electric shaver according to claim 7, wherein the mounting meanscomprises one or more spring mountings which imparts to the two cuttersections a common natural frequency of reciprocation.

9. An electric shaver according to claim 7, wherein the driving meansoperates-to drive both cutter sections .at or close to their commonnatural frequency of reciprocation.

10. An electric shaver according to claim 7, wherein said driving meansincludes a battery powered motor. 11. An electric shaver according toclaim 7, wherein said pair of devices comprisesa pair of crank throwscoupled to said crank.

12. An electric shaver comprising: at least two cutter sections movablymounted aligned with each other and in end-to-end relationship;

drive means including a motor having a rotary output shaft; I

transmission means including a crank coupled to and driven by said motorshaft and a pair of crank throws driven by said crank and being coupledto said at least two cutter sections for driving said at least twocutter sections in end-to-end reciprocation, respectively in antiphase;and

support means including mountings coupled to and resiliently supportingeach cutter section, each mounting including a spring, the springconstants (K K of the mounting springs being selected in relation to themasses (M M of the respective cutter sections so that VKJM, issubstantially equal to vK /M so that the'at least two cutter sectionshave substantially the same natural frequency of reciprocation;

said motor being operable under power to simultaneously-drive saidmovable cutter sections via said transmission means substantiallycontinuously at a frequency of reciprocation substantially equal to saidnatural frequency.

13. An electric shaver according to claim 12, wherein at least the twomovable cutter sections comprise movable inner cutters cooperating withan-outer foil.

14. An electric shaver according to claim 12, comprising two movablecutter sections and wherein said supporting means for the two cuttersections comprises a pair of leaf springs having at least two armsprojecting from a common root, at least one arm being secured at itsfree end to one section and at least oneother arm being secured at itsfree end to the other section.

15. An electric shaver according to claim 13, wherein said outer foil isstationary 16. An electric shaver according to claim 12, wherein saidmotor is a battery powered motor.

17. An electric shaver comprising: two cutter sections movably mountedin alignment in end-to-end relationship;

means for resiliently mounting the cutter sections for linearreciprocation in said aligned end-to-end relationship, said mountingmeans including resilient structures defining a natural rest positionfor each cutter section at substantially the centre of its path oflinear reciprocation; and

driving means including a motor having a rotary output shaft; and

transmission means coupled to and driven by said motor shaft, and a pairof crank throws driven by said crank and being coupled to said cuttersections so as to substantially continuously and simultaneouslyreciprocate the respective cutter sections in antiphase such that thecutter sections move simultaneously towards and away from each otheralternately and always pass substantially simultaneously through theirsaid respective natural restpositions. 18. An electric shaver accordingto claim 17, wherein said driving means includes a battery poweredmotor.

common natural frequency of reciprocation.

20. An electric shaver according to claim 17, wherein the driving meansoperates to drive both cutter sections at or close to their commonnatural frequency of reciprocation.

1. An electric shaver comprising: at least two cutter sections movablymounted aligned with each other and in end-to-end relationship; drivemeans including a motor having a rotary output shaft; transmission meansincluding a crank coupled to and driven by said motor shaft, said crankhaving a pair of devices for converting the rotary motion of said motorshaft to a linear motion, said pair of devices being coupled to said atleast two cutter sections for linearly driving said at least two alignedcutter sections in end-to-end linear reciprocation, respectively inantiphase; and support means including mountings coupled to andresiliently supported each cutter section, each mounting including aspring, the spring constants (K1,K2) of the mounting springs beingselected in relation to the masses (M1, M2) of the respective cuttersections so that Square Root K1/M1 is substantially equal to Square RootK2/M2 , so that the at least two cutter sections have substantially thesame natural frequency of reciprocation; said motor being operable underpower to simultaneously drive said movable cutter sections via saidtransmission means substantially continuously at a frequency ofreciprocation substantially equal to said natural frequency.
 2. Anelectric shaver according to claim 1, wherein the at least two movablecutter sections each comprise movable inner cutters cooperating with anouter foil.
 3. An electric shaver according to claim 2, wherein saidouter foil is stationary.
 4. An electric shaver according to claim 1,comprising two movable cutter sections and wherein said supporting meansfor the two cutter seCtions comprises a pair of leaf springs having atleast two arms projecting from a common root, at least one arm beingsecured at its free end to one section and at least one other arm beingsecured at its free end to the other section.
 5. An electric shaveraccording to claim 1, wherein said motor is a battery powered motor. 6.An electric shaver according to claim 1, wherein said pair of devicescomprises a pair of crank throws coupled to said crank.
 7. An electricshaver comprising: two cutter sections movably mounted in alignment inend-to-end relationship; means for resiliently mounting the cuttersections for linear reciprocation in said aligned end-to-endrelationship, said mounting means including resilient structuresdefining a natural rest position for each cutter section atsubstantially the centre of its path of linear reciprocation; drivingmeans including a motor having a rotary output shaft; and transmissionmeans including a crank coupled to and driven by said motor shaft, saidcrank having a pair of devices for converting the rotary motion of saidmotor shaft to a linear motion, said pair of devices being coupled tosaid cutter sections so as to substantially continuously andsimultaneously linearly reciprocate the respective cutter sections inantiphase such that the cutter sections linearly move simultaneouslytowards and away from each other alternately and always passsubstantially simultaneously through their said respective natural restpositions.
 8. An electric shaver according to claim 7, wherein themounting means comprises one or more spring mountings which imparts tothe two cutter sections a common natural frequency of reciprocation. 9.An electric shaver according to claim 7, wherein the driving meansoperates to drive both cutter sections at or close to their commonnatural frequency of reciprocation.
 10. An electric shaver according toclaim 7, wherein said driving means includes a battery powered motor.11. An electric shaver according to claim 7, wherein said pair ofdevices comprises a pair of crank throws coupled to said crank.
 12. Anelectric shaver comprising: at least two cutter sections movably mountedaligned with each other and in end-to-end relationship; drive meansincluding a motor having a rotary output shaft; transmission meansincluding a crank coupled to and driven by said motor shaft and a pairof crank throws driven by said crank and being coupled to said at leasttwo cutter sections for driving said at least two cutter sections inend-to-end reciprocation, respectively in antiphase; and support meansincluding mountings coupled to and resiliently supporting each cuttersection, each mounting including a spring, the spring constants (K1, K2)of the mounting springs being selected in relation to the masses (M1,M2) of the respective cutter sections so that square root K1/M1 issubstantially equal to square root K2/M2 , so that the at least twocutter sections have substantially the same natural frequency ofreciprocation; said motor being operable under power to simultaneouslydrive said movable cutter sections via said transmission meanssubstantially continuously at a frequency of reciprocation substantiallyequal to said natural frequency.
 13. An electric shaver according toclaim 12, wherein at least the two movable cutter sections comprisemovable inner cutters cooperating with an outer foil.
 14. An electricshaver according to claim 12, comprising two movable cutter sections andwherein said supporting means for the two cutter sections comprises apair of leaf springs having at least two arms projecting from a commonroot, at least one arm being secured at its free end to one section andat least one other arm being secured at its free end to the othersection.
 15. An electric shaver according to claim 13, wherein saidouter foil is stationary
 16. An electrIc shaver according to claim 12,wherein said motor is a battery powered motor.
 17. An electric shavercomprising: two cutter sections movably mounted in alignment inend-to-end relationship; means for resiliently mounting the cuttersections for linear reciprocation in said aligned end-to-endrelationship, said mounting means including resilient structuresdefining a natural rest position for each cutter section atsubstantially the centre of its path of linear reciprocation; anddriving means including a motor having a rotary output shaft; andtransmission means coupled to and driven by said motor shaft, and a pairof crank throws driven by said crank and being coupled to said cuttersections so as to substantially continuously and simultaneouslyreciprocate the respective cutter sections in antiphase such that thecutter sections move simultaneously towards and away from each otheralternately and always pass substantially simultaneously through theirsaid respective natural rest positions.
 18. An electric shaver accordingto claim 17, wherein said driving means includes a battery poweredmotor.
 19. An electric shaver according to claim 17, wherein themounting means comprises one or more spring mountings which impart tothe two cutter sections a common natural frequency of reciprocation. 20.An electric shaver according to claim 17, wherein the driving meansoperates to drive both cutter sections at or close to their commonnatural frequency of reciprocation.